Process and apparatus for manufacture of casein



Sept. 24, 1957 P. H. SMART Er Al. 2,807,608

PRocEss AND APPARATUS FOR MANUFAcTRE oF cAsEIN Filed March 25, 1954 I E L Confined paH-z of flow whhn which Casen precip'rl'ahon i .coalescence +3 kes p|acc.

Patented sept. 24, 1957 PROCESS AND APPARATUS FOR MANUFACTURE f F CASEIN Paul H. Smart and Carl E. yNelson, Appleton, Wis., as-

signors, by` mesne assignments, to Foremost Dairies, Inc., -San Francisco, Calif., a corporation of New York Applications/ima 2s, 1954, serial No. 418,055

1o claims. (Cl. 26o- 120) This invention relates generally `to processes and appa-y ratus for the manufacture of casein from lacteal materials, such as skim milk, which containl casein in colloidal solution. More particularly it relates to aproeess that can be used to produce a casein suitable yfor use in the manufacture of high protein milks as disclosed in co-pending application Serial No.-397,954,iiled December 14, 1953.

In the past conventional processes for the manufacture of cottage and other types of cheese have been carried out by use of batch precipitation of casein from skim milk, as distinguished from a continuous process; Batch treatment requires a relatively large number 'oftreatment steps, all of which require many hours to complete. For example in one commercial method for the manufacture of cottage cheese, the lactic acid is developed by fermentation of skim milk over a period of from live to twelve hours, and the casein precipitated by the developed acidity and added rennet. `The curd is then cutfand is rmed by heating, over a working period of from one to two hours. Removal of the whey from the curd as by decantation requires from 7 to .l5 minutes, .and subsequent washing successively with warm water, cool tap water and theni:

Referring to the'drawing: Figure 1 is a side elevational view, schematically illustrating apparatus incorporating the present invention.

Figure 2 is an enlarged cross sectional detail illustrating vthe discharge of curd and the separation of whey therefrom..r 1 A The present invention `involves the continuous ow of a lacteal material, like skim milk, through 'an elongated i confined path. 'I'heacidulation is such as to cause progressivecoagulation and precipitation of casein to take place. The `rate of flow is such as yto cause continual coalescence of precipitated casein whereby at the discharge end of the apparatus the casein is delivered in the form of a rope-like mass. j

The simple apparatus illustrated schematically in Figure 1 consists of an extended tube 10, having a mixing head chilled water, requires from 45 minutes to two hours. Following washing,.` draining of the Water requires from yone to two hours. Itis evident that such a process involves a large amount of labor which increases the cost of manufacture. The equipment employed requires a large floor area, and is relatively expensive per pound ofzcottage cheese manufactured. Because of the fermentation process and repeated handling of-the material, the resulting cottage cheese has a relatively high bacterial count.

Commercial casein has been made by both yb-atch and continuous processes. However when such vcontinuous processes are controlled to produce a casein theoretically usable for the purposes of said co-pending application, a curd is obtained which cannot be washed or treated with uniformity without excessive casein loss.

In general it is an object of the present invention to provide a continuous casein manufacturing process which produces casein curd in a form that can be readily washed without excessive loss. f f

A- further object of the invention is to provide a process of the above character which is characterized by progressive and continuous precipitation of casein and by concomitant c'oalescing of precipitated casein into a soft ycurd mass.

Another object ofthe invention is to provide a continuous process of the above character which is well adapted for the manufacture of edible Aforms of casein, including casein curd which can be readily reconstituted with milk to form a stable colloidal solution.

Another object of the invention is to pro-vide novel apparatus for carrying out the foregoing process.

Additional objects and features of the invention will appear from the following description in which the preferred in conjunction with the accompanying drawing.

11 at its inlet end. A lacteal material, such as skim milk, is supplied to the head 11kat a constant rate, and is there intermixed with acid. Storage tank 12 represents a source of skim milk which is delivered through pipe 13 at a rate controlled Iby`suitable means such as the pump 14. Heat exchanger 1'5 or other suitable heating means is provided forV maintaining the milk at a constant desired temperature level, as itis supplied Yto the mixing head. Tank 16 represents a source of dilute acid solution, which'is deliveredy to the head through a pipe 17, under the control of Valve 1.8. The rates of ow of the skim milk and acid are such. as to produce a desired and constant degree of acidulation. acidulated material flows continuously through the extended tube 10, during which time precipitation proceedsV to the point of substantial'corripletion, and coalescence of precipitated casein occurs. VIt will be evident that the tube 10 can be bent in such a manner as to occupy a minimum amount of space, `as for example zigzag fashion or helicoidally. "l

.An important feature o'f the Vpresent process is that conditions are so controlled within the extended tube 10, as to produce not only/substantially complete precipitation of casein, but also to` cause the caseinto coalesce whereby a rope-like casein curd is discharged. We have discovered that this can lbe successfully accomplished lby utilizing a controlled ilow rate through the tube 10, particularly a ow ratel which for the cross sectional llow area of the tubing, causes a condition of laminar ilow throughout the length of the tubing.

Assuming that ordinary commercial skim milk is employed which contains about 9.0% solids, the rate of acid introduction is such as to acidulate the skim milk to at or near the isoelectric point of the caseinI at the temperature employed. At temperatures ranging from 70 to 115 F., casein has an isoelectric point at about pH 4.6. In practice for the manufacture of a good quality edible casein'curd, -we have employed acidulation to a pH of 4.2 to 4.7, and preferably 4.6 to 4.7, for temperatures ranging fromto 115 F.

. The acid employed can be an inorganic acid like sulphuric or hydrochloric, or an organic acid like lactic. In any event .it is desirable to introduce ythe acid in the form of a 'dilute aqueous solution, such as 3.3% hydrochloric acid.

As previously stated, the rate of ow through the tube 10 is such as to produce certainy desired results, particu-V larly progressive precipitation of casein and coalescence of precipitated casein to form a curd of rope-like form.

proper operating range, the precipitated casein tendsto adhere to and accumulate upon the sides of the tube, thus causing clogging. When the iiow rate is greater than the proper range, turbulence is 'excessive and the precipitated particles of casein do not coalesce to form the de- From the mixing head 11 the f sired rope-like curd; When operating within a proper range of flow rate, the precipitated particles of curd gradually coalesce togetherA to produce a soft rope-like curd which flows along with the whey through the tubing as a soft flexible core. In addition to the foregoing, the lengthl of thetubingfor the flow rateemployedshould lbe such as to provide time for substantially.'complete'precipitation and coalescence.

By way `of example for 1%; inch tubing (I.A D.), good results have been secured by utilizing a flow rate within the range of from 1` to 3 litres of skim milk `per minute withacidulation to produce a pH of 4.2 to 4.7.` For the same tubing and flow rates-the length for good results can range from sixteen to thirty-forfeet, to provide total treatment-times of 22 seconds or more. Practically all of the vcurd discharging from `such `tubing is in the form of a soft rope of uniform diameter, with practically no fines. While Ms inch tubinghas `been usedwith good results, tubing of larger sizes can bev used if desired. However, it willfbe evident that larger tubing will require a greater tlow rate and a longer length.

In Figure 2 we have schematically illustrated the dis charging casein curd 2,1 as asoft rope-like mass. Itis carried `along through thetubing together with the whey, At the `discharge, endll ofjthe tube 10 the curd and the whey are `shown discharging upon the screen 22, Which maybe a drum on an endless belt` as illustrated. Whey is thus permitted to drain fromthe curd, andV the curd isrdeliveredto a tank 23 or other receiving means. Whileon the endless screenZZ the curd can be subjected to washing. Curd made in this manner can be salted or otherwise processed to form, `a product like commercial cottage cheese, or it `can be processed by other known methods to form Vvan'ousycasein or casein containing products.

In one particular instance the apparatus was constructed and operated as follows: The tubing was 3A; of an inch'in diameter (I. D.) and 20` feet long.- Skimmilk at a temperature of .105? F. was supplied to the mixing head at one end of the tubing at a llow rate of 2.8 pounds per minute. yDilute hydrochloricacidlrwassupplied to the mixinghead at a controlled rate whereby the skim milk was acidulated to about pH 4.6. Casein curd was discharged from the tubing` continuouslyin the form of a soft rope with a minimum amountof casein lines. The amount of casein thus recovered amounted to about 98.5 of the casein coagulated;

In the foregoing example the ow rate of the skim milk through the tubing provided `a AReynolds number of the order of about 2200. Higher ow rates can be used, such asrates providing a Reynolds number of the order of 4400 or higher, although the higher flow-rates tend to increase caseinlosses. In general the Reynolds number is'inlluenced by factors such'as the changing viscosity of the liquid, 1and by the varying size, shape and amount of the precipitated solids. Therefore the numbers just stated are diicult to apply numericallyto various conditions. For practical purposes it ismore satisfactory to employ a llowl rate which will provide laminar flow,'with a minimum flow time `of about 22 seconds, assuming that the conditions `are otherwise favorable for precipitation.

It will evident that thep'rocess described above makes possible the continuous manufacture of a uniform caseinI curd.' The delivered curd'isof such form that` it can be readilylwashed `withtuit excessive casein loss. All of the process is ,carriedvoutlrapidly in` closedapparatus, andtherefore there is 'limited opportunity for bacterial de.- velopment .or4 containination.` A minimum amount of labor andrsurwwisinV iS equired'ftnr operation ofthe process and-apparatus, ,The appa'rtusis relatively simple and inexpensive, and can be:` constructed to occupy a minimum amount `offloor, space. `After washing, the

ci rd" has propernes` making Ait,` desirable use in the process Qfsaid .C9-Pending, application i r r Vrlhe. capacity of :thepnaratus can` be variedasdesired. 7

4 In general greater capacity is obtained by using larger tubing of greater length. Also capacity can be increased by using two or more lengths of tubing operated in parallel, each with a separate mixing head or with a common mix- `ing head provided the flow distribution to the several tubes is equalized.

While the invention has been described as applied to skim milk, it is possible to use other liquid lacteal material which has a substantial amount of natural casein in colloidal solution. For` example the material may be skim milk from which a portion of the normal lactose content has been removed. Also it is possible to use material having a higher solids content than normal skim milk, suehaslskim milkI that has been concentrated by vacuum evaporation.

Although the invention is particularly applicable to the manufacture of a casein curd such as cottage cheese,

t the procedure can be used for the precipitation and separation o f various colloidal orsoluble materials from solution where precipitation can be caused by such factors as pH adjustment,electrolytes, heat, solvents or other precipitants*or-combinations thereof, and where the pre cipitated material has such properties that it tends to ag glomerate orucoalcsce. As examples of other colloidal solutions, referencel can bemade to aqueous protein extracts made from soybean` flour, peanut flour and cotton seed meal.

`We claim:-

l. Inca process for the manufacture of casein curd from `a lacteal material containing casein in colloidalsolution, causing an acidulatedstream of the lacteal material tollow continuously through an elongated path that conlines the stream on all sides to initiate and complete progressive precipitation of casein and to cause continuous coalescence in said path to form a moving rope-like curd mass therein.

2.` Inaprocess for `the manufacture of casein curd from a lacteal material containing casein in colloidal solution, continuously commingling a stream of the` lacteal material with a stream of acid whereby the milk is aciditied to initiate precipitationof casein, and then causing the acidilied material to flow continuously along a substantially unobstructed extended path that contines the stream on all sides with progressive precipitation of casein curd and continuous coalescence of the curd in said path to form a moving rope-like casein mass therein.

3. In a process for the manufacture of casein curd from a lacteal material containing casein in colloidal solution, continuously commingling a stream of the lacteal material with a stream of acid whereby the lacteal material is aciditied to initiate precipitation of the casein therefrom, and thencausing the combined aciditied material to flow continuously along an extended and substantially unobstructed path that confines the stream on all sides with progressive continued precipitation of the casein curd-and withuprogressive coalescence` of the curd in said path into the form of a rope-like masswhich moves continuously with the flow, delivering thc curd and the resulting Whey from' the confined path and then separating the curd from the whey.

4. A process as inrclaim 3 in which the acidified lacteal material has an acidity within the range of pH 4.2 to 4.7 after acidulation.

5. In a process for the manufacture of caseincurd from a lacteal material containing casein in colloidal solution, causing an acidulated stream of the lacteal material to flow continuously through an elongated and substantially unobstructed path concomitant with progressive precipitation of casein, the stream being confined by the path on all sides, the rate of flow through said path being controlled to cause coalescence of the precipitated material and continuous movement of the same with said ow.

6; In a process for the manufacture of casein curd from a lacteal material containing casein in colloidal solution, causing an acidulated stream of the lacteal material to flow continuously through an elongated and substantially unobstructed path concomitant with progressive precipitation of casein, the stream being confined by the path on all sides, the rate of low through said path being controlled to cause progressive coalescence of precipitated casein into the form of a rope-like mass, said mass moving along with the flow.

7. In a process for the manufacture of casein curd from normal skim milk, causing an acidulated stream of the skim milk to flow continuously through an elongated and substantially unobstructed path concomitant with progressive precipitation of casein, the stream being confined by the path on all sides, the llow velocity through the confined path being such as to provide a Reynolds number of the order of 2200 to 4400 or more, with a time period for passage through the extended path of the order of from 22 to 33 seconds or more, and continuing such flow to a point of discharge, casein curd during such flow coalescing into the form of a rope-like curd which is delivered continuously at the point of discharge.

8. A process as in claim 3 in which the stream is substantially uniform in cross-sectional flow area for substantially its entire length.

9. In a process for the manufacture of casein curd from a lacteal material containing casein in colloidal solution, continuously commingling a stream of the lacteal material with a stream of acid whereby the lacteal material is acidied to initiate precipitation of the casein therefrom, and then causing the combined acidiiied material before any substantial amount of precipitation has occurred to llow continuously along an extended and substantially unobstructed path that confines the stream on all sides with progressive continued precipitation of the casein curd and with progressive coalescence of the curd in said path into the form of a rope-like mass which moves continuously with the ow, delivering the curd and the resulting whey from the confined path and then separating the curd from the whey.

10. A process for the manufacture of a precipitated protein material from an aqueous solution of the same, the protein material being characterized by the fact that when precipitated from the solution it has properties tending to cause it to coalesce or agglomerate, continuously commingling a stream of the solution with a stream of acid, whereby the solution is acidiied to initiate precipitation of the protein material therefrom, and then causing the combined acidiiied material, before any substantial amount of precipitation has occurred, to ow continuously along an extended and substantially unobstructed path that contines the stream on all sides with progressive continued precipitation of the protein material and with progressive coalescence of the protein material in said path into the form of a rope-like curd mass which moves continuously with the ow, delivering the curd mass and the remaining liquid fraction from the confined path and then separating the curd mass from the liquid fraction.

References Cited in the tile of this patent UNITED STATES PATENTS 1,112,722 Scharf Oct. 6, 1914 1,716,799 Shefeld June 11, 1929 1,992,002 Chappell Feb. 19, 1935 2,044,282 Chickner June 16, 1936 2,099,379 Spellacy Nov. 16, 1937 2,278,670 Rauer Apr. 7, 1942 2,369,095 Wendt Feb. 6, 1945 

10. A PROCESS FOR THE MANUFACTURE OF A PRECIPITATED PROTEIN MATERIAL FROM AN AQUEOUS SOLUTION OF THE SAME, THE PROTEIN MATERIAL BEING CHARACTERIZED BY THE FACT THAT WHEN PRECIPITATED FROM THE SOLUTION IT HAS PROPERTIES TENDING TO CAUSE IT TO COALESCE OR AGGLOMERATE, CONTINUOUSLY COMMINGLING A STREAM OF THE SOLUTION WITH A STEAM OF ACID, WHEREBY THE SOLUTION IS ACIDIFIED TO INITIATE PRECIPITATION OF THE PROTEIN MATERIAL THEREFROM, AND THEN CAUSING THE COMBINED ACIDIFIED MATERIAL, BEFORE ANY SUBSTANTIAL AMOUNT OF PRECIPITATION HAS OCCURED, TO FLOW CONTINUOUSLY ALONG AN EXTENDED AND SUBSTANTIALLY UNOBSTRUCTED PATH THAT CONFINES THE STREAM ON ALL SIDES WITH PROGRESSIVE CONTINUED PRECIPITATION OF THE PROTEIN MATERIAL AND WITH PROGRESSIVE COALESCENCE OF THE PROTEIN MATERIAL IN SAID PATH INTO THE FORM OF A ROPE-LIKE CURD MASS WHICH MOVES CONTINUOUSLY WITH THE FLOW, DELIVERING THE CURD MASS AND THE REMAINING LIQUID FRACTION FROM THE CONFINED PATH AND THEN SEPARATING THE CURD MASS FROM THE LIQUID FRACTION. 